An index apparatus for an NC machine tool is disclosed in U.S. Pat. Nos. 4,991,463 and 6,455,798 to the inventor of the application.
In the apparatus of U.S. Pat. No. 4,991,463, the NC machine tool includes a spindle, a main table and an NC device for making a machining relative movement between the spindle and the main table. The apparatus includes a housing mounted on the main table. The apparatus further includes an index table on which a work is held, the index table being supported on the housing for rotation. The apparatus is a push bar type which includes a push bar extending into the housing and outwardly of the housing for longitudinal movement. The NC device is arranged to make an extra relative movement between the spindle and the main table other than the machining relative movement, so that the push bar can be pushed and moved longitudinally thereof by the extra relative movement. Transmission means is received in the housing and disposed between the push bar and the index table to rotate the index table at an angle in response to the movement of the push bar whenever the push bar is moved, so as to index the work.
However, the apparatus cannot always stop the index table exactly, after rotating the index table at the angle. The index table may be rotated by momentum. Accordingly, the apparatus cannot always index the work exactly.
In the apparatus of U.S. Pat. No. 6,455,798, an additional push bar extends into the housing and outwardly of the housing in addition to the push bar, the push bar or the additional push bar being pushed and moved longitudinally thereof by the extra relative movement. Transmission means is received in the housing and disposed between the push bar, the additional push bar and the index table to rotate the index table in one direction in response to the movement of the push bar and in the reverse direction in response the movement of the additional push bar, so as to index the work.
However, the index apparatus also cannot always stop the index table exactly, after rotating the index table at the angle. The index table may be rotated by momentum.
It is therefore an object of the invention to provide a new push bar type of index apparatus which can stop the index table exactly, after rotating the index table at an angle, to index a work exactly.